Why not a film camera with an EVF?

[Alan Edward Klein]

That doesn't quite explain the modern f/1.4 - f/1.8 primes we see pop up all the time specifically for mirrorless camera systems.

It;s an ego thing or they're not aware of how small DOF is at such large apertures. Also, you carry around a heavier lens that costs more because of all that extra glass.

If you shoot a "standard" 50mm at f/1.4 on a full frame camera of someone's upper body from 5 feet, (roughly 2 1/2' x 3 1/2' field of view) you only have less than 3" DOF. That's less than 1 1/2" in front and in back of the focal point. So if you focus on the eyes, the subject's ears and tip of the nose will be out of focus. IF his head is at an angle, the second eye will also be out of focus. IF your focus is slightly off, even the eyes will be out of focus. f/4.0 will give you about 8" DOF.

In fairness, at ten feet, the field of view of 5' x 7' approx, you have almost a 12" DOF at f/1.4. SO you may want that. But in most cases, f/1.4 just isn;t needed with modern cameras as much as the old low ISO film SLRs with OVFs.

 

[koraks]

It;s an ego thing or they're not aware of how small DOF is at such large apertures.

I'm not so sure. That sounds like a bit of a harsh judgement on the decision making of people you apparently didn't know that existed.

Most of the arguments I see from them are in the direction of the quality of unshrapness rendering (bokeh), the ability to use relatively low ISO even under adverse lighting conditions but also other attributes of the lens that do not directly relate to the maximum aperture, like build quality, focus speed/precision etc.

As to the argument of "need": most photos aren't really needed anyway. That argument almost never goes anywhere. Most of us do it for enjoyment; it's inherently irrational.

 

[wiltw]

I can visualize a resulting print or slide far more effectively using an optical viewfinder image - which I have decades of experience with - than if presented with the image on what amounts to a very close, very small computer screen.
I expect most reasonably competent film photographers would be in the same boat.
Perhaps you are aiming your product idea at photographers who are only just moving to film from earlier experience with digital cameras with EVFs or nothing but live view on a screen. If so, I don't know whether that will help them with the transition to film or not - I expect it might actually impede the process.
One chooses a viewing system based on how well one uses it to visualize the result.
Histograms and the like are probably useful additions, but not if they get in the way of seeing + visualizing.
Garry Winogrand's line comes to mind:
"I photograph to see what the world looks like photographed"
Optical viewfinders seem to do a bit better job of giving most of us here a bit better of a sneak peek of the result ahead of time.

One of the key factors in judging DOF is the acuity of human vision to detect blur circles ('blurry'rather than be fooled into assessing a blur circle as a perceived 'dot' ('sharp' enough). It is a know fact that standard 'manufacturer DOF' assumes human visual acuity which is WORSE than what optometrists around the world aim to achieve in correcting our vision...human eyes can detect one half minute of arc! The assumption behind DOF tables and most programs is not 20/20 vision (6/6 in Europe), so they typical DOF table is a LIE vs. the reality of what the person with 20/20 actually sees in an 8x10" photo assessed from a viewing distance of 10". It is well known that the EVF of most cameras presents fewer pixels than our cameras capture...IOW the resolution of the EVF is not as good as it needs to be...the presentation of the CofC in the viewfinder itself is NOT a precise presentation by the limitations of the resolution of the LCD. Admittedly even the OVF of the typical dSLR lies to us, as the coarseness of the standard dSLR screen only permits good assessment of focus equivalent to f/4 lens at best, not the f/1.4 lens which might be mounted.
As for presentation of an image with 'accuracy' to reflect what is captured, even that is 'colored' by whatever parameters are in effect to process RAW into viewable JPG on the LCD, and those parameters are not matching the parameters we choose to use during RAW conversion and postprocessing back at home! IOW, yet another visual LIE from the reality of the final print.
Yes, an EVF presents much more than is presented in any film viewfinder in real time, relative to the final print. But the OVF is a better presentation of realtime reality of the scene itself than an EVF over the false reality of the EVF mimicing the captured image, even though the film SLR presents nothing relative to the captured image. And that is what is appealing to most photographers expressing the preference of the OVF over a pricey EVF retrofit.

 

[wiltw]

The push for very bright and expensive lenses has really been eliminated with EVF and high ISO sensors used in mirrorless digital cameras.

but the EVF and high ISO capture does not eliminate the desire for the isolations permitted by extremely shallow DOF, which is one reason for the f/1.4 lens. And desired precision of focus, even using autofocus, is inherently better from the shallower DOF using larger focusing aperture. And the larger shooting aperture will permit better motion freezing than what a smaller max aperture lens would force in the same low light conditions. The reason for big apertures is lessened but not 'eliminated' as stated.